Hatch opening and closing on oxygenation and deoxygenation of C60 bathysphere

The structures and stabilities of C60On, where n=1–6, 9, have been calculated using the AM1 Hamiltonian and the program mopac 6.0, and by the density functional technique B3LYP/6-31G* at the AM1 geometry using Gaussian 98. Modes of oxygen addition considered were ethers, epoxides, ketones and ketenes. It is confirmed that in C60O a carbon–carbon bond on a pent–hex edge is replaced by an ether linkage. For higher levels of oxygen addition the replacement of a carbon–carbon bond by two ketone groups becomes important. Particularly stable structures are formed if the additions are on the same, or adjacent, C6 rings of the C60 structure where the oxygen atoms cooperate in opening up large holes in the molecule. Molecules of greatest stability have a mixture of ether oxygen atoms on pent–hex edges and diketone additions on hex–hex edges. A particularly important stable structure is the mixed ether/ketone isomer of C60O6 in which a hinged C5O2 hatch lid containing two ketone oxygen atoms is opened revealing a hatch 4–5 Å in diameter. An even larger hole of approximately 6 Å in diameter is opened up in a particularly stable isomer of C60O9 which contains three ether and six ketone groups. Removal of the oxygen atoms from these structures and reoptimisation leads to hatch closing and C60 is reformed.